Method of installing a fastener to a panel

ABSTRACT

An installation apparatus and method of attaching a female element, such as a nut, to a panel, wherein the panel is pierced and the female element is permanently installed in the pierced panel opening in a continuous operation. The female element includes a body portion and an annular barrel portion. In one of the methods disclosed, the panel is pierced by the free end of the barrel portion and the panel slug is disposed in the barrel portion as the nut is installed in the panel. In the presently preferred method, the panel is pierced by a punch received through the body and barrel portions, prior to driving the female element into a mechanical interlock with the panel. In the preferred installation, the free end of the barrel portion is deformed into a hook-shaped end portion, opening toward the body portion, and the panel is simultaneously driven into the hook-shaped barrel end portion, forming a very secure mechanical interlock. The preferred installation apparatus includes an annular plunger which drives the female element into the panel and which is reciprocally supported in a chamber in a base member attached to one die member of a press. A punch is located within the annular plunger which pierces the panel prior to driving the female element into the panel, as described.

This application is a continuation-in-part application of co-pendingapplication Ser. No. 563,833, filed Dec. 23, 1983, now U.S. Pat. No.4,555,838, which application was a continuation-in-part application ofSer. No. 485,099, filed Mar. 28, 1983, now U.S. Pat. No. 4,459,073, andSer. No. 504,074, filed June 14, 1983, now abandoned which applicationswere, respectively, divisional and continuation applications of Ser. No.229,274, filed Jan. 28, 1981, now abandoned. Ser. No. 229,274 claimspriority to an application filed Feb. 2, 1980 in the Federal Republic ofGermany, No. 3003908.

FIELD OF THE INVENTION

The present invention relates to methods of attaching a female element,particularly female fastener elements such as a nut, to a panel, whereinthe panel is pierced and the female element is installed in the piercedpanel opening in a continuous operation and an installation apparatus.

The prior art includes self-piercing nuts, which may also besimultaneously clinched to secure the nut in the pierced panel opening,such as disclosed in U.S. Pat. Nos. 3,299,500 and 3,314,138, assigned tothe assignee of the instant application. The prior art also includes anumber of self-riveting nuts, including nuts having an annular skirt orbarrel portion wherein the free end of the barrel portion is deformedradially outwardly in a die member to form a mechanical interlock withthe panel, see for example U.S. Pat. Nos. 3,938,239 and 4,018,257. Theself-riveting nuts disclosed in such patents are, however, secured to apanel having a prepierced panel opening, requiring two separateoperations. Such methods also require very precise centering of the nutrelative to the prepierced panel opening, limiting the integrity of theinstallation, particularly in production applications. U.S. Pat. No.3,926,236, which is assigned to the assignee of the instant application,discloses a method of attaching a nut wherein the panel is pierced by apunch which extends through the nut bore to pierce and secure the nut ina continuous operation, however, the fastener is not a riveting typefastener having a barrel portion extending through the pierced panelopening. Reference is also made to U.S. Pat. No. 3,800,401 whichdiscloses a method of making a container closure such as a tag ring, ina continuous application. It is understood that the prior art alsoincludes various riveting techniques and methods wherein the fastenerelement includes an annular end portion, which may be press fittedthrough an opening in a panel, which is then riveted or deformedradially outwardly in a die member having an annular semi-toroidal diecavity, which may include a projecting central die portion whichreceives the annular riveting end of the fastener. The prior art alsodiscloses means of attaching stud-like fasteners, wherein the studincludes an annular end portion which penetrates a plate or structuralmember, which may be deformed radially outwardly. Examples of such priorart are cited in the above identified copending application.

The method of attaching a female element or fastener of the presentinvention forms a unique and improved assembly, particularly inrelatively thin panels such as presently used in the automotive andappliance industries. The methods of this invention are performed in acontinuous operation and are particularly suitable for application in adie apparatus or press having relatively moveable press members, whereinthe installation apparatus is attached to the die members within thepress. The die press may be utilized to simultaneously form the panelinto any desired configuration, making the method and installationapparatus of this invention particularly suitable for mass productionapplications. Several female elements or fasteners may be installed witheach stroke of the die press, eliminating the requirement for secondaryoperations including prepiercing the panel.

SUMMARY OF THE INVENTION

As described, the method of this invention may be utilized topermanently install a female element or fastener in a panel in acontinuous operation. The female element utilized in the method of thisinvention includes a body portion, an annular barrel or skirt portionwhich extends from the body portion having a free open end, and a borewhich extends through the body portion, preferably in coaxial alignmentwith the opening through the barrel portion. The female element may be anut having a threaded or unthreaded bore, a bearing or similar element.

The method of this invention includes first locating the female elementadjacent a panel with the barrel portion free end facing the panel readyfor installation; then, piercing a slug from the panel, forming apierced panel opening coaxially aligned with the body portion bore andbarrel portion opening. The method then includes driving the barrelportion of the female element through the pierced panel opening,preferably drawing a tubular panel portion from the plane of the panel,then deforming the barrel portion free end radially outwardly. Finally,the preferred method includes deforming the barrel portion free endtoward the body portion into a U-shaped annular channel which openstoward the body portion and simultaneously driving the panel portioninto the developing U-shaped barrel portion channel and deforming thepanel portion in the channel to form a secure mechanical interlockbetween the panel and the female or fastener element.

In the method first disclosed in the above identified copendingapplication, the female element annular barrel portion free end includesa piercing surface adjacent the opening to the annular barrel portion.The method includes piercing a slug from the panel with the barrelportion piercing surface. The panel slug is then disposed with theannular barrel portion to prevent collapse of the barrel portion as thepanel is deformed against the exterior surface of the barrel portion andformation of the U-shaped channel portion at the free end of the barrelportion. The panel slug is then removed from the assembly by a punchreceived through the bore of the body portion.

The preferred method of installation first disclosed in this applicationincludes piercing a slug from the panel with a punch disposed throughthe body portion bore, which removes the slug from the assembly prior todriving the free end of the female element barrel portion into thepanel. This method simplifies the installation apparatus and providesother advantages, as described below. In either method, however, thefemale element may be attached to the panel in a continuous operationand the panel is pierced prior to driving the female element into thepierced panel opening and forming the preferred mechanical interlockdescribed.

After the fastener element is located relative to the panel as describedready for installation, the barrel portion free end is preferably biasedagainst the panel to preload the panel prior to piercing. Thisaccurately locates the female element relative to the panel and assuresconcentricity of the final assembly, which is very important to theintegrity of the mechanicl interlock. Where the panel is pierced with apunch disposed through the female element body portion bore, theinternal diameter of the bore is preferably less than the internaldiameter of the barrel portion opening. The punch then pierces a slugfrom the panel having a diameter less than the internal diameter of thebarrel portion, providing additional panel in the mechanical interlock.The method then includes driving the female element barrel portion freeend against the panel adjacent the pierced opening, wherein the panel ispreferably entrapped beneath the barrel portion free end, drawing thepanel from the plane of the main panel portion. As described herein, themechanical interlock between the panel portion adjacent the piercedpanel opening and the female element is performed in a die member or diebutton. The preferred die button includes a smooth annular die cavitywhich deforms the free end of the barrel portion radially outwardly,preferably into the hook or U-shaped annular channel described and acentral projecting portion which is telescopically received within thefemale element barrel portion opening during the formation of themechanical interlock. The central projecting portion also supports thepanel portion adjacent the pierced panel edge during piercing and thepanel portion is drawn over the central projecting portion of the die bythe free end of the barrel portion, thinning the panel portion as thepanel portion is driven into the annular die cavity.

In the most preferred method of this invention, the body portion of thefemale element has an external dimension which is greater than theexternal dimension of the barrel portion and the body portion includesan annular bottom wall or surface which faces the panel. The bottom wallof the body portion preferably includes a plurality of projecting ribswhich provide antirotation means for the female element and improve theassembly as now described. The preferred method then includes drivingthe ribs into the panel portion adjacent the pierced panel edge,following receipt of the panel portion in the developing U-shapedchannel at the free end of the barrel portion, and then driving thebottom wall of the body portion into the panel portion which has beenreceived in the U-shaped barrel portion, increasing the mechanicalinterlock.

The preferred embodiment of the installation apparatus disclosed hereinis particularly adapted for performing the newly disclosed method ofinstallation, wherein the panel is pierced by disposing a punch throughthe bore in the female element body portion, prior to driving the femaleelement into the panel, as described. The apparatus includes a basemember which is adapted to be fixed relative to one die member of a diepress having opposed relatively moveable die members. An annular plungeris reciprocably supported in the base member having a shank portionwhich extends through an opening in the base member. The apparatus alsoincludes a nose member which is normally spaced from, but moveabletoward the base member, having a plunger passage which telescopicallyreceives the shank portion of the plunger. The nose member also includesa second passage which intersects and communicates with the plungerpassage for receiving female elements for installation by the apparatus.The annular plunger has an axial guide passage extending therethroughwhich telescopically receives a piercing punch. The piercing punch hasan axial length greater than the plunger and the piercing punch is fixedrelative to the base member. In the disclosed embodiment, one end of thepiercing punch is attached to the die member to which the base member isattached. The plunger is normally biased into the plunger passage of thenose member by a biasing or spring means, such that the free ends of theplunger and piercing punch are generally aligned adjacent the secondpassage in the nose member, such that a fastener element may be receivedin the plunger passage and aligned ready for installation opposite theplunger and punch members. The installation apparatus also includes anactuating means which relatively closes the base and nose members uponreceipt of a female element aligned in the plunger passage ready forinstallation. In the disclosed embodiment of the installation apparatus,the base and nose members are relatively closed by closing the diepress.

The disclosed embodiment of the installation apparatus performs themethod of this invention, as follows. Relative closing movement of thenose and base members extends the plunger and piercing punch into theplunger into the plunger passage of the nose member. The annular freeend of the plunger first engages the opposed end of the fastener elementbody portion, biasing the barrel portion free end against a panellocated opposite the plunger passage under the force of the biasingmeans. The piercing punch simultaneously extends into the bore of thefemale element body portion to engage the panel. The punch then piercesa slug from the panel, which is driven out of the assembly through thebore in the die button, as described above. Finally, the female elementis driven into the panel by the plunger and installed in the piercedpanel opening, as described above.

In the preferred embodiment of the installation apparatus, the basemember includes a chamber and the plunger includes an enlarged headportion which is reciprocably supported in the base member chamber. Thebiasing means may then be located in the base member chamber, normallyextending the plunger shank portion into the nose member plungerpassage. In the preferred embodiment of the disclosed installationapparatus, the biasing means is pneumatic pressure. The apparatusincludes a source of pneumatic pressure which maintains a predeterminedpressure in the base member chamber. The pneumatic pressure escapesbetween the annular plunger and the piercing punch to the free ends ofthe plunger and punch members. This creates a vacuum adjacent the secondpassage in the nose member, drawing a female element from the secondpassage toward the plunger and centering the female element in theplunger passage, ready for installation. As will be understood, thefemale element must be accurately aligned in the plunger passage forreceipt of the punch through the bore of the body portion. The vacuumcreated by the pneumatic biasing means assures the alignment required.

Other advantages and meritorious features of the method of attaching afemale element to a panel and installation apparatus of this inventionwill be more fully understood from the following description of thepreferred embodiments and the drawings, a brief description of whichfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cross-sectioned bottom elevation of one embodimentof a self-attaching female element of nut fastener which may be utilizedin the method of attachment and installation apparatus of thisinvention;

FIG. 2 is a partially cross-sectioned side view of one embodiment of theinstallation apparatus of this invention installing the nut fastenershown in FIG. 1 in a panel;

FIG. 3 is a partially cross-sectioned side view of the installationapparatus shown in FIG. 2 in the final step of the installation;

FIG. 4 is a partially cross-sectioned top elevation of a secondembodiment of a nut fastener which may be utilized in the method ofinstallation and installation apparatus of this invention;

FIG. 5 is a partially cross-sectioned side view of a second embodimentof the installation apparatus of this invention ready to install a nutfastener as shown in FIG. 4;

FIG. 6 is a partially cross-sectioned side view of the installationapparatus shown in FIG. 5 during an initial step in the method ofinstallation of this invention;

FIG. 7 is a partial enlarged side cross-sectional view of theinstallation apparatus as shown in FIG. 6;

FIG. 8 is a partial enlarged side cross-sectional view of theinstallation apparatus shown in FIGS. 5-7 illustrating a further step ofthe method of installation of this invention;

FIG. 9 is a partially cross-sectioned side view of the installationapparatus shown in FIGS. 5 and 6 illustrating a further step of themethod of installation of this invention;

FIG. 10 is a partial enlarged side cross-sectional view of theinstallation apparatus as shown in FIG. 9;

FIG. 11 is a partial enlarged side cross-sectional view of theinstallation apparatus shown in FIGS. 5-10 illustrating a further stepin the method of installation of this apparatus;

FIG. 12 is a partial enlarged side cross-sectional view of theinstallation apparatus shown in FIGS. 5-11 illustrating a further stepin the method of installation of this invention;

FIG. 13 is a partial enlarged side cross-sectional view similar to FIG.12 illustrating the final step of the method of installation of thisinvention;

FIG. 14 is a partial side cross-sectional view of the installationapparatus shown in FIGS. 5, 6 and 9 illustrating the position of theinstallation apparatus following installation of a nut fastener; and

FIG. 15 is a partially schematic cross-sectional view of FIG. 5 in thedirection of view arrows 15--15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description of the preferred embodimentsreferences copending U.S. patent application Ser. No. 563,833, filedDec. 21, 1983, the disclosure of which is incorporated herein byreference. FIGS. 1 to 3 of this application are taken from the abovereferenced copending application and disclose the then preferredembodiment of the self-piercing and riveting nut fastener, installationapparatus and method of installation. This application discloses animproved alternative method of attaching a modified self-riveting femaleelement of nut fastener and a detailed description of the preferredembodiments of the installation apparatus and method of this invention.As used herein, female elements is intended to be generic to elementshaving a threaded or unthreaded bore, which is preferably coaxiallyaligned with the opening in an integral annular barrel portion,including self-riveting nuts, rivets, bearing elements and the like. Thedisclosed are both nut fasteners for ease of description.

The self-piercing and riveting nut fastener 20 shown in FIG. 1 includesa body portion 22 and an annular barrel portion 24. The body portion 22includes an annular driving surface 26 and a bore 28 through the drivingsurface and coaxially aligned with the opening 30 through the barrelportion. The body portion includes a bottom wall 32 adjacent the barrelportion 24 which includes a plurality of radially projecting ribs 34.The anti-rotation ribs 34 are generally triangular including a portionintegral with the tubular barrel portion 24. The barrel portion 24 has afree end 36 which, in the disclosed embodiment, includes a relativelysharp piercing surface 38 at the opening 30 of the tubular barrelportion and an arcuate drawing surface 40.

As described more fully in the above referenced copending patentapplication, the self-piercing and riveting fastener 20 is adapted topierce the panel and be permanently installed in the pierced panelopening. FIGS. 2 and 3 disclose the working components of one embodimentof an installation appartus adapted to install the nut fastener shown inFIG. 1. The nut fastener 20 is first located adjacent a panel 42 withthe free end 36 of the barrel portion 24 facing the panel. A die memberor die button 44 is located on the opposite side of the panel from thenut fastener. As shown, the die button 44 includes an annular orsemi-toroidal die cavity 47. A shoulder 45 surrounds the die cavity 47which supports the main portion of the panel 42. The disclosedembodiment of the die button includes a bore 46 and a center die member48 in fixed relation supported in the die button bore 46 during theinstallation of the nut fastener. As shown, the center die member 48includes a conical end portion 50 which projects from the center of theannular die cavity 47.

The self-piercing and riveting nut 20 is centered in an installationapparatus opposite the die cavity 47 with the nut bore 28 coaxiallyaligned with the center die member 48. The installation apparatusincludes a reciprocal annular plunger 52 having a center bore 54 and anannular end portion 56. In the disclosed embodiment, a ram or punch 58is located in the bore 54 of the plunger. The annular end portion 56 ofthe plunger 52 drives the free end 36 of the nut fastener 20 into thepanel 42. As described more fully in the above referenced copendingapplication, the piercing surface 38 pierces a slug 60 from the panelwhich is received and centered on the conical end portion 50 of thecenter die member 48. The free end 36 of the barrel portion 24 of thenut fastener is then received against the semi-toroidal surface of theannular die cavity 47 which deforms the free end 36 of the barrelportion 24 radially outwardly into a hook-shaped end portion or U-shapedannular channel 24a. The panel portion 42a adjacent the pierced panelopening is first deformed against the exterior surface of the annularbarrel portion 24 as the barrel portion is received through the piercedpanel opening. The panel portion 42a is then deformed into thedeveloping U-shaped barrel portion 24a by the annular bottom wall 32 ofthe body portion 22 and finally, the ribs 34 are driven into the panelportion 42a as shown in FIG. 2. As the annular wall 24 is driven intothe annular die cavity 47 the slug 60 is moved upwardly into the opening30 in the annular barrel portion 24 such that the slug 60 supports thetubular barrel portion 24 at the point of greatest stress, preventingthe annular barrel portion from collapsing inwardly during the rivetingstep. Thus, the slug 60 performs an important function in the method ofinstallation the self-piercing and riveting nut fastener 20 shown inFIGS. 2 and 3. Further, the resultant nut and panel assembly forms anextremely rigid and secure mechanical interlock wherein the panelportion 42a is locked in the U-shaped channel 24a formed in the free end36 of the nut fastener and the bottom wall 32 of the body portion 22.Further, the location of the projecting ribs 34 in the annular bottomwall 32 does not weaken the assembly, but serves to further deform thepanel portion 42a, as shown.

Following installation, the slug 60 is driven out of the assembly by ramor punch 58 as shown in FIG. 3. As will be understood, the nut fasteneris installed in the panel in a continuous operation after the nut islocated in the installation apparatus opposite the panel, as described.Further, as described, the installation apparatus may be located in adie press, such as used by the automotive industry to form panels. Insuch an application, the head assembly including the reciprocal plunger52 is attached to one die member or platen and the die button 44 isattached to the opposed die member. In a down-pierce installation, theinstallation head is attached to the upper die shoe and the die buttonis attached to the lower die shoe. It will be understood, however, thatthe assembly may be reversed in an up-pierce application. The termsupper and lower, top and bottom, are therefore relative terms and areused herein for descriptive purposes only.

FIG. 4 illustrates an improved self-riveting nut fastener 70 which isspecifically adapted for installation by the type of apparatus disclosedin the following figures. As will be noted, the self-riveting nut 70 isof the same general configuration as the nut fastener 20 describedabove. The nut fastener includes a body portion 72 and an annular ortubular barrel portion 74. The body portion includes an annular drivingsurface 76 and a threaded bore 78 coaxially aligned and communicatingwith the opening 80 through the barrel portion. The bottom wall orannular surface 82 of the body portion includes a plurality of radialprojecting ribs 84 and the free end 86 of the barrel portion 74 includesa chamfered surface 88 and an arcuate drawing surface 90.

As will be understood from the detailed description of the installationapparatus and method of installing the self-riveting nut fastener 70,the panel is pierced and the panel slug is driven out of the assembly bya punch received through the nut bore 78 prior to installing the nut inthe pierced panel opening. Thus, the panel slug is not received in theopening 80 of the tubular barrel portion 74 to support the barrelportion during the riveting step. The barrel portion 74 has thus beenmodified by providing a chamfer 88 adjacent the opening 80 on the freeend 86 of the barrel portion and the barrel portion has been shortenedto avoid collapse during the riveting step. An arcuate surface may alsobe used in place of the chamfered surface 88.

The installation apparatus disclosed in FIG. 5 and the remaining figuresis adapted to be secured within a die press having opposed moveableplatens or die members. The female elements to be installed in the panelare received in a head assembly 100 having a base member 102 which maybe attached to the upper die member or die shoe 104. As will beunderstood by those skilled in the art, the head assembly is normallyattached to a backing plate 106 which includes the fastening means forattaching the head assembly to the upper die shoe. Normally, the headassembly 100 is attached to the backing plate 106 and the backing plateis attached to the upper die shoe 104 by bolts, screws or otherconventional fastening means. As set forth above, however, the assemblymay be reversed in an up-pierce application, wherein the head assembly100 is attached to the lower die shoe.

The head assembly 100 includes an annular plunger 108 having an enlargedpiston-like head portion 110 which reciprocates in a chamber 112 and thebase member includes an opening 114 through which the plunger extends.In the disclosed embodiment, the plunger 108 is cylindrical and thechamber 112 and passage 114 are also cylindrical to support thereciprocal motion of the plunger. It will be understood, however, thatthe cross-sectional configuration of the plunger will depend upon theparticular application. The disclosed embodiment of the self-rivetingfastener 70 is also generally cylindrical, however, the shape of the nutfastener will also depend upon the particular application. For example,the body portion 72 of the nut fastener may be hexagonal or octagonaland the shape of the barrel portion 74 may also be modified provided,however, that the bore 78 of the female element body portion ispreferably coaxially aligned with the opening 80 in the barrel portion.

The head portion 110 of the plunger is sealed within the chamber 112 byO-rings 116 and 118 on the plunger head portion 110 and at the end ofthe chamber, respectively. An orienting pin 120 is provided in thedisclosed embodiment to prevent rotation of the plunger. The orientingpin includes a flat surface which slideably engages a flat surface ofthe plunger, preventing rotation of the plunger relative to the basemember 102. A piercing punch 122 is disposed within the opening 123which extends through the annular plunger. In the disclosed embodiment,the piercing punch includes a head 124 which is attached to the backingplate 106, opposite the head portion 110 of the plunger. The piercingpunch 122 is therefore fixed relative to the base member 102 and theplunger 108 may move relative to the base member 102 and the piercingpunch 122, within the chamber 112.

The head assembly 100 also includes a nose member 126 which movesrelative to the base member 102 during installation of the femaleelements 70 as described hereinbelow. The nose member includes a plungerpassage 128 which receives the shank portion 130 of the plunger 108 andthe included piercing punch 122. The nose member also includes atransverse second passage 132 which communicates with the plungerpassage for receipt for female elements, such as the nut fasteners 70.In the disclosed embodiment, the nut fasteners 70 are received through aplastic chute 134, which is attached to the nose member by a chuteadapter 136. Access to the chute adapter is provided by a cover plate138 which is attached to the chute adapter by screws or other fasteningmeans. The nose member 126 is supported on the base member 102 by aguide cylinder 139 which guides the movement of the nose member relativeto the base member. A stop pin 140 is provided which limits the spacebetween the nose member and the base member and the nose member isnormally spaced from the base member by a spring means, not shown. Inthe disclosed embodiment, a cavity 142 has been provided in the upperdie shoe which receives the end of the guide cylinder 139 when the nosemember moves toward the base member and a spacer block 144 is providedbetween the nose member 126 and the base member 102 to accurately limitthe relative movement. As will be understood the general construction ofthe nose member 126 and base member 102, including the cylinder guide139, stop pin 140 and the biasing spring assembly are known in the artand are utilized in pierce nut installation heads as disclosed in thepatents assigned to the assignee of the instant application, includingU.S. Pat. Nos. 3,098,576, 3,718,965 and 3,942,235, which areincorporated herein by reference.

A predetermined air pressure is maintained in the plunger chamber 112 byan air line 146, which is attached to the backing plate 106 by a fitting148, and the backing plate includes an air passage 150 which providescommunication between the air line 146 and the chamber 112. In a typicalapplication, the line 146 is attached to the line pressure normallyavailable in a manufacturing plant, which is generally between 40 and 70PSI. The pneumatic pressure in the chamber 112 provides a biasing meanswhich normally biases the plunger 108 into the plunger passage 128 ofthe nose member 126. In this position, the free ends of the plungershank portion 130 and the piercing punch 122 are generally alignedadjacent the second passage 132 of the nose member, providingcommunication between the second passage 132 and the plunger passage128, as shown in FIG. 5. The nut fastener is normally retained in theplunger passage, opposite the plunger and piercing punch, in the readyposition 70a, by spring biased fingers, not shown, as described in theabove referenced patents.

A panel 160 is located opposite the installation head on the lower dieshoe 158. The installation die button 154 is located in the lower dieshoe 158 coaxially aligned with the plunger passage 128, the plunger 108and piercing punch 122. In the disclosed embodiment, the die button 154includes a die button insert 156 which projects from the center of thedie button, as disclosed more fully hereinbelow. Further, the panel issupported on conventional spring biased stripper pins 162 which assistin the stripping of the nut and panel assembly from the die button aswill be understood by those skilled in the art. Further, in thedisclosed embodiment, the actuating means for the installation apparatusincludes a conventional magnetic proximity switch located in the nosemember 126, nor shown, which indicates whether a nut fastener is locatedin the ready position 70a. The lead wire for the proximity switch isshown at 152. The conventional magnetic proximity switch is normallylocated opposite the second passage 132. When a nut fastener is locatedin the ready position, 70a, the proximity switch enables the actuationof the die press, wherein one of the die members or shoes is movedtoward the other die shoe, installing a nut fastener in the panel. In atypical application, the upper die shoe 104 is moved toward the lowerdie shoe 158, as now described with the remaining figures.

Upon downward movement of the upper die shoe 104, the nose member 126first engages the panel 160, biasing the stripper pins 162 toward thedie button 154 and reducing the space between the nose member 126 andthe base member 102 as shown in FIG. 6. This relative movement extendsthe plunger shank portion 130 into the plunger passage 128 to engage theannular driving surface 76 of the body portion 72 of the nut fastener,moving the nut fastener from the ready position to the panel, as bestshown in FIG. 7. In this position, the panel 160 is firmly clampedbetween the nose member 126 and the shoulder 170 of the die button 154or the panel is clamped to the lower die shoe. The free end 86 of thenut barrel portion 74 is biased against the panel by the shank portion130 of the plunger member 108, preloading the panel. As described above,the plunger is resiliently biased into the plunger passage by thepneumatic pressure in the base member chamber 112. As shown in FIG. 6,the plunger head portion 110 has not yet moved in the chamber 112,however the pressure of the free end 86 of the nut fastener against thepanel is sufficient to slightly indent or mark the panel, which isimportant to accurately coaxially align the nut barrel portion 74 withthe annular die cavity 172 in the die button 154 and maintain theconcentricity of the nut and panel assembly during the installation ofthe nut fastener.

As best shown in FIG. 7, the die button 154 includes a semi-toroidal diecavity 172 and the die button insert 156 includes a projecting endportion 174 which smoothly continues the annular concave surface of thedie cavity. A stepped bore 178 extends through the die button insert,which is coaxially aligned with the piercing punch 122. In the disclosedembodiment, the die button insert 156 is press fitted into the bore 180in the die button 154 and the die insert includes an enlarged endportion 182 which accurately locates the insert in the die button. Aswill be understood by those skilled in the art from the followingdescription of the method of installation, the projecting end 174 of thedie button insert is subject to wear and therefore a separatereplaceable insert has been used. It will be understood, however, thatthe die button may be an integral unit as disclosed in the abovereferenced copending application.

In the relative positions of the base and nose members 102 and 126 shownin FIG. 6, the piercing punch 122 is extended through the nut bore 78 ofthe body portion 72 and the opening 80 through the barrel portion 74 toengage the panel as shown in FIG. 7. As set forth above, the free end 86of the barrel portion 74 is biased against the panel by the plungershank portion 130, preloading the panel and maintaining the coaxialalignment of the tubular barrel portion 74 with the annular die cavity172. Continued closing of the die press moves the nose member 126 towardthe base member 102 because the nose member is bottomed on the lower dieshoe 158, as shown in FIG. 6. The piercing punch 122 therefore movesrelative to the plunger 108, through the opening 123 in the plunger,biasing the panel into the annular die cavity 172 in the die button andagainst the projecting end portion 174 of the die button insert 156, asshown in FIG. 8. As will be noted, the free end 86 of the nut fastenerbarrel portion 74 maintains the preload condition against the panel, asdescribed above. The panel 160 remains clamped between the shoulder 170of the die button 154 and the nose member 126.

Continued relative closing of the die press causes the piercing punch122 to extend through the panel and pierce a slug 184 from the panel asbest shown in FIG. 10. In this position, as shown in FIG. 9, the headportion 110 of the plunger head portion 110 remains slightly spaced fromthe backing plate 106, such that the plunger is not yet fixed relativeto the base member 102, however, the free end 86 of the barrel portion74 remains preloaded against the panel under the pneumatic pressure inthe plunger chamber 112. The panel is pierced between the chamferedopening to the bore 178 in the die button insert 156 and the outer edgeof the piercing punch 122 and the panel slug 184 is immediately removedfrom the assembly into the bore 178 of the die button insert.

When the plunger head 110 bottoms against the backing plate 106, theshank portion 130 of the plunger drives the free end 86 of the barrelportion 74 into the panel portion 160a adjacent the pierced panelopening as shown in FIG. 11. The panel portion 160a is initiallyentrapped beneath the free end 86 of the barrel portion and the convexsuface of the projecting end portion 174 of the die button insert,slightly thinning the panel portion and drawing the panel portion intothe annular die cavity 172. As the plunger continues to drive the nutfastener into the die cavity 172, the free end 86 of the barrel portion74 engages the bottom semi-toroidal surface of the die cavity 172,deforming the barrel portion free end radially outwardly as shown inFIG. 12 at 86a. The panel portion adjacent the pierced panel opening issimultaneously drawn against the exterior surface of the barrel portion74 into a tubular configuration 160b, as shown in FIG. 12. Finally, thefree end of the annular barrel portion is turned toward the body portion72 of the nut fastener against the surface of the die cavity 172 into aU-shaped channel 86b, which is hook-shaped in cross section as shown inFIG. 13. The annular surface of the female element bottom wall 82 issimultaneously driven into the panel, deforming the panel portion in thedeveloping U-shaped channel 86b and enlarging the end of the panelportion, as shown at 160c in FIG. 13. Further, the projecting ribs 84 onthe bottom wall 82 of the body portion are driven into the panel portion160c, providing antirotation means for the nut fastener in the panel andfurther deforming the panel portion in the hook-shaped end portion 86bof the barrel portion. The nose member 126 is now fully seated againstthe base member 102 as shown in FIG. 14. That is, the base member 102has bottomed against the spacer block 144, limiting the relativemovement between the nose member 126 and the base member 102. Further,the guide cylinder 139 has moved into the cavity 142 in the upper dieshoe 104.

The assembly between the female element 70 and the panel 160 is nowcomplete. Upon opening of the die press, the base member 102 is firstlifted with the upper die shoe 104 until the nose member 126 is fullyspaced from the base member as shown in FIG. 5. As described above, thebase and nose members are normally spaced by a spring or other biasingmeans. In the disclosed embodiment, a spiral spring is located in theguide cylinder 139 biased against the upper die shoe 104. The nosemember 126 is then lifted off of the assembly and the stripper pins 162lift the panel from the shoulder 170 of the die button. The feedmechanism, not shown, then feeds a fastener element from the secondpassage 132 in the nose member 126 to the plunger passage 128 to theready position 70a shown in FIG. 5. Various feed and chuck systems aredisclosed in the above referenced patents. A gravity feed may also beutilized, particularly in the disclosed installation apparatus whichincludes a vacuum assist, as now described.

As shown in FIG. 5 and 15, a vacuum is created adjacent the second nutpassage 132 which draws a female element 70 adjacent the plunger passageinto the plunger passage 128 and centers the female element relative tothe piercing punch 122 and plunger 108. The pneumatic pressure in thechamber 112 supplied by air line 146 escapes between the piercing punch122 and the plunger 108 through the opening 123 though the plunger.Because the space between the piercing punch 122 and the plunger 108 issubstantially less than the volume of the chamber 112, the velocity ofthe air increases. When a female element is not located in the plungerpassage 128, the air escapes through the plunger passage 128, creating avacuum adjacent the second passage 132. This reduced pressure tends todraw a fastener 70 from the second passage into the plunger passage asshown in FIG. 15, which is a compound cross-sectional view used toillustrate the pressure differential acting on a nut in the secondpassage. In actual operation, a small nut fastener 70 will be drawn intothe plunger passage 128 by the vacuum described. More importantly, thevacuum serves to center a nut fastener of the type disclosed beneath theplunger and piercing punch, assuring orientation of a female element inthe plunger passage, ready for installation. This feature of theinstallation apparatus of this invention is particularly useful in agravity feed system.

Having described the preferred embodiments of the female element and theinstallation apparatus, it is now possible to summarize the preferredmethods of installation. As described above, the preferred method ofinstallation includes first locating a female element adjacent a panelwith the free end of the barrel portion facing the panel. In the methodof attachment shown in FIGS. 1 to 3, the free end 36 of the barrelportion 24 includes a piercing surface 38 which pierces a slug 60 fromthe panel, forming a pierced panel opening which is coaxially alignedwith the body portion bore 28 and the opening 30 through the barrelportion. With the embodiment of the female element 70 shown in FIG. 4,the panel is pierced by a piercing punch 122 which is disposed throughthe body portion bore 78 and the opening 80 through the barrel portion74. Next, the female element barrel portion is driven through thepierced panel opening. In FIGS. 1 to 3, the plunger 52 drives the freeend 36 of the barrel portion 24 into the panel to first pierce the panel42 and then the free end 36 of the barrel portion is driven through thepierced panel opening to deform the barrel portion free end radiallyoutwardly. The panel portion 42a is simultaneously deformed against theexterior surface of the barrel portion 24 into a tubular configuration,drawing the panel portion from the plane of the panel 42.

In the installation method disclosed in FIGS. 5 to 14, the plunger shankportion 130 first biases the free end 86 of the barrel portion 74against the panel 160, preloading the panel as shown in FIG. 7. Thecenter punch 122 then deforms the panel into the die cavity 172 toengage the projecting end 174 of the die insert 156 while the panelremains preloaded by the free end 86 of the barrel portion, as shown inFIG. 8. The panel is then pierced by the center punch 122 and the panelslug 184 is removed from the assembly, prior to driving the free end 86of the barrel portion into the panel, as shown in FIG. 10. The free end86 of the barrel portion is then driven into the panel, entrapping thepanel portion 160a beneath the free end of the barrel portion andslightly thinning the panel portion, as shown in FIG. 11. The free endof the barrel portion is then driven through the pierced panel openingand against the concave annular wall of the die cavity 172, deformingthe free end of the barrel portion radially outwardly as shown at 86a inFIG. 12. As noted above, the panel portion adjacent the pierced panelopening is simultaneously drawn into a tubular configuration 160bagainst the exterior surface of the barrel portion 74.

Finally, in the most preferred method of this invention, the free end ofthe barrel portion is deformed into a U-shaped annular channel whichopens toward the body portion and the panel portion adjacent the piercedpanel opening is simultaneously deformed in the developing U-shapedbarrel portion to form a secure mechanical interlock between the paneland the female element. As described above in regard to FIGS. 1 to 3,the free end 36 of the barrel portion 24 of the female element isdeformed against the concave annular wall of the die cavity 47 into aU-shaped channel 24a and the panel portion 42a is deformed within thehook-shaped portion, forming a secure mechanical interlock. Followingformation of the nut and panel assembly, the slug 60 is driven out ofthe assembly, as shown in FIG. 3. In the method of installation shown inFIG. 13, the free end 86b of the barrel portion is similarly deformedinto a U-shaped channel portion and the panel portion 160c is deformedwithin the barrel portion channel, securely retaining the panel portion,as described above.

Having described the preferred embodiments of the method of attaching afemale element to a panel and the preferred embodiments of theinstallation apparatus of this invention, it will be understood thatvarious modifications may be made to the method and the installationapparatus within the purview of the appended claims. The configurationand dimensions of the self-riveting female fastener, for example, willdepend upon the particular application and the panel thickness. Asdescribed above, the disclosed female elements and methods of attachmentof this invention are particularly adapted for permanent attachment ofthe female element to relatively thin panels, such as utilized forstructural components in the automotive and appliance industries. Forexample, the female element may be attached to relatively thin panelshaving a thickness of approximately 0.025 inches to relatively thickpanels for the automotive industry having a thickness of 0.125 inches.The dimensions of the female element will, of course, depend upon thethickness of the panel and the particular application. A female element,such as a self-riveting nut, may be formed of medium carbon steels.Further, the configuration of the body portion of the female elementwill depend upon the preferred application. Thus, the body portion maybe of any suitable configuration and the barrel portion may becylindrical, hexagonal, etc. The female elements may be formed byconventional hot or cold forming methods.

I now claim:
 1. A method of attaching a female element to a panel, saidfemale element having a body portion an annular barrel portion extendingfrom said body portion having a free open end, and a bore extendingthrough said body portion in generally coaxial alignment with theopening in said barrel portion, said method comprising the followingsteps performed in a continuous sequence:(a) locating said femaleelement adjacent a panel with said barrel portion free end facing saidpanel; (b) biasing said female element barrel portion free end againstsaid panel, preloading said panel; (c) piercing a slug from said panelwith a punch disposed through said body portion bore and said annularbarrel protion opening while the panel portion adjacent the piercedpanel opening remains under load; (d) driving said female element barrelportion free end into said panel and through said pierced panel opening;and (e) deforming said barrel portion free end radially outwardlyforming a U-shaped portion in cross section and disposing said panelportion adjacent said pierced panel opening into said U-shaped portionin mechanical interlocking relation.
 2. The method of attaching a femaleelement to a panel as defined in claim 1, characterized in that theinternal diameter of said female element body portion bore is less thanthe internal diameter of said barrel portion opening, said punchtelescopically received through said body portion bore, said punchpiercing a slug from said panel with said pierced panel opening having adiameter less than the internal diameter of said barrel portion, saidmethod then comprising driving said barrel portion free end against saidpanel portion adjacent said pierced panel opening, entrapping said panelportion beneath said barrel portion free end, thinning said panelportion, then driving said barrel portion free end through said piercedpanel opening.
 3. The method of attaching a female element to a panel asdefined in claim 1, characterized in that said female element bodyportion having an external dimension greater than the exteral dimensionof said barrel portion, said body portion having an annular bottom walladjacent said barrel portion facing said panel, said body portion bottomwall including a plurality of projecting ribs, said method includingdeforming said barrel portion free end into a hook-shaped end portionopening toward said body portion, driving said ribs into said panelportion following receipt of said panel portion in said barrelhook-shaped end portion, and then driving said body portion bottom wallinto said panel portion, increasing said mechanical interlock.
 4. Amethod of attaching a female element to a plastically deformable panel,said female element having a body portion, an annular plasticallydeformable barrel portion extending from said body portion having a freeopened end, and a bore extending through said body portion communicatingwith the opening through said barrel portion, the internal diameter ofsaid body portion bore being less than said barrel portion opening, saidmethod comprising the following steps performed in a continuousoperation:(a) locating said female element adjacent a panel with saidbarrel portion free end facing said panel and a die member located onthe opposite side of said panel, said die member having an annular diecavity surrounding a central projecting die portion having a centralaperture therethrough coaxially aligned with said female element bodyportion bore and barrel portion opening; (b) piercing a slug from saidpanel with a punch disposed through said body portion bore and saidannular barrel portion opening, said punch then extending into said diemember central portion aperture, removing said panel slug from theassembly; (c) driving said female element barrel portion free endagainst the panel portion adjacent the pierced panel opening, deformingsaid panel portion into said die cavity; and (d) continuing to drivesaid female element barrel portion free end through said pierced panelopening and against the bottom wall of said die cavity, plasticallydeforming said barrel portion free end into a U-shaped end portion incross-section, simultaneously driving said panel portion into saidbarrel portion U-shaped end portion, plastically deforming andincreasing the thickness of said panel portion to substantially conformto and substantially fill said U-shaped barrel portion, andsimultaneously deforming and interlocking said barrel portion free endwith said thickened panel portion forming a mechanical interlock.
 5. Themethod of attaching a female element to a panel as defined in claim 4,characterized in that said die member includes a panel supportingshoulder on opposed sides of said die cavity and said central projectingdie portion is spaced below the plane of said panel supporting shoulder,said method including first deforming said panel into said die cavity toengage said central die portion, then piercing a slug from said panelwith said punch.
 6. The method of attaching a female element to a panelas defined in claim 4, including biasing said female element barrelportion free end against said panel, preloading said panel, prior topiercing a slug from said panel and piercing a slug from said panelwhile said panel portion remains under load.
 7. The method of attachinga female element to a panel as defined in claim 4, wherein said methodincludes entrapping said panel portion beneath said barrel portion freeend, thinning said panel, then driving said barrel portion free endthrough said pierced panel opening.
 8. The method of attaching a femaleelement to a panel as defined in claim 4, characterized in that saidfemale element body portion having an external diameter greater than theexternal diameter of said barrel portion, said body portion having anannular bottom wall adjacent said barrel portion facing said panel, saidbody portion bottom wall including a plurality of projecting ribs, saidmethod including driving said ribs into said panel portion followingreceipt of said panel portion in said barrel portion hook-shaped endportion and then driving said body portion bottom wall into said panelportion, thereby increasing said mechanical interlock.
 9. The method ofattaching a female element to a panel as defined in claim 4, whereinsaid panel portion is initially drawn into said die member cavityentrapped beneath said barrel portion free end, following piercing ofsaid panel by said punch.
 10. A method of attaching a female element toa plastically deformable panel, said female element including a bodyportion and an annular plastically deformable barrel portion extendingfrom said body portion having a free open end, said body portion havinga bore extending therethrough coaxially aligned and communicating withthe opening through said annular barrel portion, said method comprisingthe following steps performed in a continuous operation:(a) locatingsaid female element adjacent a panel with said barrel portion free endfacing said panel; (b) piercing a slug from said panel and forming apierced panel opening coaxially aligned with said female element bodyportion bore and barrel portion opening; (c) driving said female elementbarrel portion through said pierced panel opening; (d) plasticallydeforming the panel portion adjacent said pierced panel opening againstsaid free end and the exterior surface of said annular barrel portion,drawing a tubular panel portion from the plane of said panel into saidannular die cavity; (e) deforming said female element barrel portionfree end radially outwardly; and (f) deforming said female elementbarrel portion free end toward said body portion into a U-shaped annularchannel opening toward said body portion, simultaneously driving saidpanel portion into the developing U-shaped barrel portion channel,plastically deforming said panel portion in said U-shaped channel andincreasing the thickness of an end of said drawn panel portion anddeforming said barrel portion free end against said enlarged panelportion forming a secure mechanical interlock between said panel andsaid female element.
 11. The method of attaching a female element to apanel as defined in claim 10, wherein said method includes piercing aslug from said panel by disposing a punch through said body portion boreand barrel portion opening, then driving said barrel portion free endagainst said panel portion and through said pierced panel opening.
 12. Amethod of attaching a self-fastening element to a generally planarplastically deformable panel in a die member, said self-fasteningelement having a body portion and an integral annular barrel portionhaving a free open end portion, said body portion hving a side surfaceand a bottom surface and said annular barrel portion integrally joinedto said body portion bottom surface spaced inwardly from said sidesurface, said die member having an annular die cavity including anarcuate concave annular die cavity surface and a central projecting dieportion telescopically and closely receivable in said self-fasteningelement annular barrel portion, said panel including a generallycircular opening having an internal diameter less than the externaldiameter of said self-fastening annular barrel portion, the methodcomprising the following steps performed in a continuous operation:(a)driving said self-fastening element barrel portion free end against saidpanel and through said panel opening plastically deforming the panelportion adjacent said panel opening into said annular die cavity anddisposing said self-fastening element annular wall around said diemember central projecting die portion; (b) plastically deforming saidself-fastening element annular barrel portion free end radiallyoutwardly into a U-shaped channel in cross section opening toward saidbody portion against said arcuate concave annular die cavity surface;and (c) simultaneously driving said self-fastening elment body portionbottom surface into said panel adjacent said panel portion, driving saidpanel portion into the developing U-shaped portion of said barrelportion free end and against the bottom surface of said U-shaped channelplastically deforming and increasing the thickness of said panel portionin said U-shaped channel, and deforming said barrel portion free endagainst said thickened panel portion forming a secure mechanicalinterlock between said self-fastening element annular barrel portionfree end and said panel portion.
 13. The method of attaching aself-fastening element as defined in claim 12, wherein saidself-fastening element is a female element having a bore extendingthrough said body portion coaxially aligned with the opening throughsaid annular barrel portion, the method including driving a punchthrough said self-fastening element body portion bore and barrelportion, said punch piercing a slug from said panel and forming saidpanel opening, then driving said self-fastening barrel portion free endthrough said panel opening.
 14. A method of attaching a self-fasteningelement to a plastically deformable panel in a die member, saidself-fastening element having a body portion and an annular barrelportion having a free open end portion, said annular barrel portionhaving an inner surface terminating in an annular outwardly angledchamfer surface at said free open end portion, said die member having apanel supporting surface on at least opposed sides of an annular concavedie cavity configured to receive said self-fastening element annularbarrel portion and a central die portion projecting from said concavedie cavity telescopically receivable in said annular barrel portion freeopen end portion, said central die portion having an outer surfaceconfigured to be closely received in said barrel portion, said centraldie portion having a free end spaced below said panel supporting surfacewithin said annular die cavity, the method comprising the followingsteps performed in sequence:(a) supporting a plastically deformablepanel on said die member panel supporting surface and locating saidself-fastening element opposite said panel with said annular portionfree end facing said panel generally concentrically aligned with saiddie member central portion; (b) driving said self-fastening elmementbarrel free end, drawing said panel into said annular die cavity againstsaid die member central portion free end, pre-loading said panel; (c)piercing a slug from said panel and forming a pierced panel openingcoaxially aligned with said annular barrel portion having an insidediameter less than the external dimension of said central projecting dieportion outer surface; (d) driving said self-fastening element free endagainst said panel, drawing, rolling and thinning the panel portionadjacent said pierced panel opening between said barrel portion annularchamfer surface and said die member central portion outer surface; and(e) driving said barrel portion free end through said pierced panelopening into said annular die cavity, telescopically receiving said diemember central portion in said annular barrel portion free end, andplastically deforming said barrel portion annular free end radiallyoutwardly and forming a mechanical interlock with said panel portion.15. The method of attaching a self-fastening element as defined in claim14, wherein said method includes driving said annular barrel portionfree end against a smooth concave bottom surface of said annular diecavity, plastically deforming said free end into a U-shaped channel incross-section and simultaneously driving said panel portion into thedeveloping U-shaped channel to substantially fill said channel and forma secure mechanical interlock.